David C":39tmwez7 said:
I am afraid the logic is incorrect.
I judge camber by the light showing at either edge when the blade is offered up to a straight block of industrial plastic.
For squaring edges with a 2 3/8" blade this gap might be 10 or 12 thou".
If the timber is particularly dense and prone to tearout, K&K suggest a C/B setting of around 4 thou".
This leads to the outer edges of the C/B being over the edge of the blade. Something that I am not happy with.
This is solved by slight camber on the C/B which has no ill effects.
It may not be necessary in some people's view, but it is easy to do and has no down side.
This is not some theoretical argument, I have done it for many years.
David Charlesworth
David, you're still in the weeds. I don't debate you can work with the setup that you're using. You seem to be convinced that you've solved a problem and that my logic is lacking, but you have less depth in this subject and you don't realize it.
I figured when you brought this up that you were referring to a cosmetic issue (and you are - the fact that the cap iron goes past the edge of the iron is of no consequence in actual use, and you haven't yet figured that out). At some point you will.
As far as the downside goes, if you've taken a hundredth off of the cap iron at the edges, the plane has lost the ability to control tearout on a straight ground blade without gaining any additional capability on a cambered iron.
One other aside, and that is that Kato and Kawai never prescribed 4 thousandth for any hand tools. The professors who did the work were very specific that the testing shown in the video (and the related paper) is to support development of machine planers (like the super surfacer). They wrote a separate paper that was intended to help people set the cap iron on a hand plane and it says no more than to suggest that examination of the quality of the shaving (when it begins to straighten) and the resulting surface are key for setting a cap iron properly. In practical use, there is never or nearly never a time that a cap iron on a hand plane should be set to 4 thousandths of an inch.
If you ever were to try to do that, you'd never get the part of the iron that you've cambered in the cut, anyway. The plane would become too difficult to push and not stay in the cut before you got to a shaving thickness equal to the cap iron set (you'd be only 1/3rd or 1/4th of the way to the parts you've doctored ever even seeing the cut). But beyond that yet, unless the mouth on your plane is large and the wear sloping away, you can't even get the cap iron down to the level of the sole, let alone beyond. It can only come within a few thousandths of an inch of striking distance.
As far as practical, I've been using the cap iron to reduce tearout since before there was any cap iron videos from K&K. When the video came out, I figured there'd be people who would take it too literally and believe they could or should set a cap iron equal to shaving thickness. I was in contact with Bill Tindall before the university who owned the videos ever even made them available - they were effectively locked away because they didn't want them to be available in the public domain. I was goaded by warren mickley, that's the reason I learned to use the cap iron, and goaded by the realization that people knew more about using planes 200 years go when they had to do it to eat. I rode the wave of "small improvements" before that for a while, including in making my own infill planes, only to find out I should've been paying more attention to how people did things when they had to be good at them to survive. I don't refer to theory, I refer to practice. Some things in practice are superior to others. In this case, you're on the wrong side of it, but the consequences are small, you're lucky.
